The overall objectives of this project include the autoradiographic localization of various narcotic agonists and antagonists in brain and the myenteric plexus of the guinea pig ileum. The localization and binding of 3H-morphine, 3H-etorphine, 3H-enkephaline and the antagonist 3H-naloxone are being studied in the myenteric plexus of naive and addicted animals using in vitro preparations. The distribution of binding sites of these narcotic agonists and antagonists in the myenteric plexus will be studied with relation to biogenic amines and acetylcholine localization as a function of the contractile response in isolated ileum. BIBLIOGRAPHIC REFERENCES: Autoradiographic Studies of 3H-Morphine. M. Watanabe, I.M. Diab, C.R. Schuster and L.J. Roth. In: Tissue Responses to Addictive Drugs," Editors: Donald H. Ford and Doris Clouet, Spectrum Publications, Holliswood, New York,1976, Autoradiography in Cytopharmacology. L.J. Roth, I.M. Diab, M. Watanabe, and R.J. Dinerstein. In: Methods in Drug Metabolism Research. Editors: Jean L. Hirz and Edward R. Garrett. Marcell Dekker, Inc. New York, 1977.